基于施密特过程的变量筛选及其在森林覆盖率分析中的应用

在多元线性回归模型的实际应用中,因受分析人员主观判断的影响,初始选取的自变量集合往往会包含过多的变量。本文利用施密特过程提出一种新的变量筛选方法,可以选择对因变量有显著解释作用的自变量,并且将没有解释作用的信息及冗余信息有效地分解出来并排除掉。将该方法应用于森林覆盖率影响因素分析,有效地进行了变量筛选,并得到了解释性很强同时拟合优度较高的模型结果。     

内生区位与独占厂商空间定价策略分析

在有关独占厂商空间定价的研究中,许多文献假定市场范围外生给定。为在可变市场范围假定下,得到更为一般性的结论,放松买者固定概率分布假定,研究需求型态和买者分布型态与定价策略优劣的关系。研究发现,当市场范围内生决定时,厂商利润大小,与需求函数型态有关,而与买者分布无关,拓展了有关研究;消费者剩余和社会福利在FOB定价下恒大于CIF定价,与需求型态和买者分布均无关,与以往文献不同。     

Identification of Marginal Effects in Nonseparable Models Without Monotonicity

Nonseparable models do not impose any type of additivity between the unobserved part and the observable regressors, and are therefore ideal for many economic applications. To identify these models using the entire joint distribution of the data as summarized in regression quantiles, monotonicity in unobservables has frequently been assumed. This paper establishes that in the absence of monotonicity, the quantiles identify local average structural derivatives of nonseparable models.     

Modeling categorical covariates for lifetime data in the presence of cure fraction by Bayesian partition structures

In this paper, we propose a Bayesian partition modeling for lifetime data in the presence of a cure fraction by considering a local structure generated by a tessellation which depends on covariates. In this modeling we include information of nominal qualitative variables with more than two categories or ordinal qualitative variables. The proposed modeling is based on a promotion time cure model structure but assuming that the number of competing causes follows a geometric distribution. It is an alternative modeling strategy to the conventional survival regression modeling generally used for modeling lifetime data in the presence of a cure fraction, which models the cure fraction through a (generalized) linear model of the covariates. An advantage of our approach is its ability to capture the effects of covariates in a local structure. The flexibility of having a local structure is crucial to capture local effects and features of the data. The modeling is illustrated on two real melanoma data sets.     

Simple Formula for Calculating Bias‐corrected AIC in Generalized Linear Models

In real‐data analysis, deciding the best subset of variables in regression models is an important problem. Akaike's information criterion (AIC) is often used in order to select variables in many fields. When the sample size is not so large, the AIC has a non‐negligible bias that will detrimentally affect variable selection. The present paper considers a bias correction of AIC for selecting variables in the generalized linear model (GLM). The GLM can express a number of statistical models by changing the distribution and the link function, such as the normal linear regression model, the logistic regression model, and the probit model, which are currently commonly used in a number of applied fields. In the present study, we obtain a simple expression for a bias‐corrected AIC (corrected AIC, or CAIC) in GLMs. Furthermore, we provide an ‘R’ code based on our formula. A numerical study reveals that the CAIC has better performance than the AIC for variable selection.     

股权结构变量对企业财务危机影响的实证研究

企业经营管理中客观存在的风险有可能导致企业财务危机的发生,因此有必要建立财务危机预警模型,以便及时地进行财务危机预警分析,及早地发现财务危机信号。为了有效地设计财务危机预警模型解释变量项,以我国125家工业企业上市公司为研究对象,根据我国上市公司的股权结构现状及有关法规,研究了股权结构变量对企业发生财务危机的影响。以因财务状况异常而被特别处理(ST)的公司作为发生财务危机的界定标准,运用Logistic回归分析对选取的上市公司股权结构变量进行了筛选,发现部分股权结构变量对企业的财务危机有着显著的影响。     

Consistent Bayesian information criterion based on a mixture prior for possibly high-dimensional multivariate linear regression models

In the problem of selecting variables in a multivariate linear regression model, we derive new Bayesian information criteria based on a prior mixing a smooth distribution and a delta distribution. Each of them can be interpreted as a fusion of the Akaike information criterion (AIC) and the Bayesian information criterion (BIC). Inheriting their asymptotic properties, our information criteria are consistent in variable selection in both the large-sample and the high-dimensional asymptotic frameworks. In numerical simulations, variable selection methods based on our information criteria choose the true set of variables with high probability in most cases.     

A New Specification Test for the Validity of Instrumental Variables

We develop a new specification test for IV estimators adopting a particular second order approximation of Bekker. The new specification test compares the difference of the forward (conventional) 2SLS estimator of the coefficient of the right‐hand side endogenous variable with the reverse 2SLS estimator of the same unknown parameter when the normalization is changed. Under the null hypothesis that conventional first order asymptotics provide a reliable guide to inference, the two estimates should be very similar. Our test sees whether the resulting difference in the two estimates satisfies the results of second order asymptotic theory. Essentially the same idea is applied to develop another new specification test using second‐order unbiased estimators of the type first proposed by Nagar. If the forward and reverse Nagar‐type estimators are not significantly different we recommend estimation by LIML, which we demonstrate is the optimal linear combination of the Nagar‐type estimators (to second order). We also demonstrate the high degree of similarity for k‐class estimators between the approach of Bekker and the Edgeworth expansion approach of Rothenberg. An empirical example and Monte Carlo evidence demonstrate the operation of the new specification test.     

Confidence limits for conformance proportions in normal mixture models

Conformance proportions are important numerical indices for quality assessments. When the population is characterized by a normal mixture model, estimating conformance proportions can be a practical issue. To account for the inherent structure of normal mixture models, universal and individual conformance proportions are first defined for the purpose of evaluating the overall population and specific subpopulations of interest, respectively. On the basis of generalized fiducial quantities, a systematic method is then proposed in this paper to obtain confidence limits for the two classes of conformance proportions. The simulation results demonstrate that the proposed method can maintain the empirical coverage rate sufficiently close to the nominal level. In addition, two examples are given to illustrate the proposed method.     

FDI对物流产业竞争力的影响研究

为研究中国FDI与物流产业竞争力之间相互关系,在1997~2014年FDI和物流产业统计数据的基础上,运用协整检验和Granger因果检验展开定量分析。研究认为,物流产业FDI与物流产业竞争力存在长期负向相关关系,而非物流产业FDI与物流产业竞争力存在长期正向相关关系;物流产业竞争力是导致物流产业FDI的Granger原因,反之不成立,非物流产业FDI是导致物流产业竞争力变动的Granger原因,反之亦不成立;研究结果表明,FDI通过技术路径与劳动资本密集度路径对物流产业竞争力构成正向影响,通过资本路径以及行业就业人员占比路径对物流产业竞争力提升构成阻碍。